This invention relates generally to clamps and more specifically to a retracting power clamp.
It is often desirable to forcibly clamp and hold an item in a predetermined position or location in order to perform a machining or fabrication operation on the item. In such applications, the complexity of the shape or configuration of the item being clamped often presents difficulties in clamping the item and providing access for a clamping member to engage the item. Thus, it has been found advantageous to provide clamping devices having clamping components or mechanisms that are capable of being extended either for horizontal or vertical clamping engagement of the item. It is also known to employ clamps that have gripping arms that can be retracted into the body of the clamp in order to clear the path for other operations or to temporarily unobstruct an area for moving the item between adjacent conveyed locations. One such device is disclosed in U.S. Pat. No. 5,165,670 entitled "Retracting Power Clamp" which issued to Sawdon on Nov. 24, 1992; this device weighs approximately 13 pounds.
Other conventional power clamps typically employ a piston cylinder which is separately formed and attached to an inverted L-shaped linkage housing. Such conventional linkage housings are commonly formed of flat cast or extruded side plates having a rectangular cross sectional shape. For example, DE-STA-CO Company Model No. 8005-7F clamp, which weighs approximately 12 pounds (for a 11.06 inch long by 2.36 inch thick by 5.51 inch wide clamp), has a linkage housing which significantly overhangs and is larger than the separate piston cylinder; this DE-STA-CO clamp is further believed to use at least two linkages having first ends pivotably joined to a retracting arm and having second ends pivotably joined to the linkage housing. A Tunkers GmbH clamp Model No. PKS 50 U, also has a linkage housing which significantly overhangs a separate piston cylinder; this device weighs approximately 9.9 pounds (for a 11.34 inch long by 2.36 inch thick by 4.72 inch wide clamp). U.S. Pat. No. 4,494,739 which issued to Valentine and U.S. Pat. No. 3,545,050 which issued to Blatt et al. also disclose other arrangements of clamps employing separate linkage housings and piston cylinders.
In accordance with the present invention, the preferred embodiment of a retracting power clamp includes a body having a generally cylindrical external surface. A clamping arm is movable from a retracted position to a clamping position with the arm being linearly extendable and pivotable relative to the body when moved between the retracted and clamping positions. In another aspect of the present invention, the arm is entirely located inside the body when in the retracted position and the arm is entirely located external to the body when in the clamping position. A further aspect of the present invention provides a sleeve linearly movable in the body, a piston driven rod linearly movable in said sleeve and a link which couples the arm to the driving rod while the arm is also pivotably coupled to the sleeve. In yet a further aspect of the present invention, the body is machined as a single piece including a piston chamber and a receptacle for linkages. Still another aspect of the present invention utilizes a spring biased plunger for selectively engaging a detent in the sleeve to encourage the sleeve and arm to remain in a fully retracted position if fluid pressure is lost.
The retracting power clamp of the present invention is highly advantageous over traditional clamps by utilizing a single piece body having a circular-cylindrical external shape. This allows for lower manufacturing cost. This body arrangement also promotes quicker setting up and manufacturing of the present invention clamp while also allowing for mounting adjustability to an infinite variety of linear and rotational use positions relative to a stationary manufacturing plant fixture. The clamp of the present invention is also more compact and lighter weight (approximately 8.5 pounds for a 11.73 inch long and 2.953 inch diameter clamp) than most other known retracting clamps due to the circular shape and fewer number of clamp components. Standard gripper pads, common with other clamps and grippers, can be quickly and easily attached and removed to the end of the clamp arm of the present invention. Furthermore, the present invention uses fewer linkages than many other clamps, thus reducing part and assembly costs while improving durability and part tolerance build-ups. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.